CAIRO (AP) — Teenager Gehad Mustafa wears an ultraconservative veil over her face and was raised in a family of staunch Muslim Brotherhood supporters. Yet for the past weeks, she has been walking though chaotic street markets and crowded subway stations, collecting signatures on a petition demanding Islamist President Mohammed Morsi step down.

The months-long petition campaign by the group “Tamarod,” Arabic for “rebel,” is now culminating in nationwide protests Sunday in which the opposition hopes to bring out millions to force Morsi out of office, a year after his inauguration.

But Tamarod’s organizers say they are not stopping there. No matter what happens on Sunday, they say they have created through their petition drive a real grassroots network, an opposition version in the spirit of the Islamists’ expert street organizing, and have brought forth a sort of second generation of street activists, like Mustafa, after the first that led the revolt against autocrat Hosni Mubarak in 2011.

They want to use that network going ahead, to keep the public involved and to pressure the secular and liberal opposition parties, who the activists say have wasted opportunities through infighting and fragmentation, to get their act together.

On a recent day, Tamarod’s main office, steps away from Cairo’s Tahrir Square, was bustling with several dozen volunteers as young as 13 and as old as their 50s and 60s. University professors, government employees, students and housewives sipped tea, smoked and chatted while going through the organization’s prize possession: the sheaves of signed petitions still coming in from around the country, filling the office.

The pages of signatures, they say, are proof of how deeply the country of 90 million has turned against the Muslim Brotherhood. They plan to announce their full count ahead of Sunday’s protests but have claimed to have as many as 20 million signatures, which they collate, confirm and record in a database in a precise operation, knowing their count will be questioned.

Among the volunteers was 17-year-old Mustafa. She said she turned against Morsi and his Muslim Brotherhood after the first protesters were killed under his administration in late 2012. “I saw the reality,” she said. “You told us that the blood of the martyrs will not go in vain. But there were more … falling under your rule.”

She joined Tamarod, which launched in late April, and volunteered to canvas the street for signatures. At one point, while passing out petitions in the subway, a man wearing the beard of a Muslim conservative attacked her, pulling the veil off her face. But other commuters then wrestled the man away in support of her.

“This strengthened me. I felt what I am doing is right,” she said.

Organizers say Tamarod mushroomed across the country. Founded by five activists, its leadership is a central group of about 25, connected to a network of coordinators in Egypt’s 27 provinces, each with a team of volunteers in towns and villages.

The signatures are effectively a database of the dissatisfied: Each signatory puts his or her name, province of residence and national ID number.

Collecting signatures in itself is a breakthrough, overcoming Egyptians’ engrained resistance to signing onto any paper presented by a stranger, especially political, from the Mubarak days when doing so could get you a visit from state security or even arrested. Volunteers carrying the petitions brought politics into every corner — weddings, slum alleys, buses and subways. Volunteers included strangers to political campaigning, from men selling cigarettes in kiosks to impoverished women selling in vegetable markets.

Ahmed el-Masry, one of the founders of Tamarod, calls the success “astonishing.”

“I can’t tell how many members out there. I can think that millions of Egyptians are members,” he said.

“At one point, people gave up (on Morsi) … it reached a point where a new class of Brothers are gaining higher status in society that to join them, you have to let your beard grow. We reached a point where no one is heard but the president and his tribe.”

Brotherhood officials cast doubt on the signatures, claiming forgeries and multiple names. While Morsi says peaceful demonstrations are a legitimate form of expression, he and his allies also say Mubarak loyalists are behind the campaign and protests, trying to use the streets to topple an elected leader.

A spokesman for the Brotherhood’s Freedom and Justice Party said he sympathizes with some activists in Tamarod — “the young revolutionaries who had great expectations out of the revolution. Due to their inexperience and age, they wanted to see change too fast and too soon and that is what I call frustration.”

But Abdel-Mawgoud el-Dardery said “opportunist politicians” are exploiting them for their political agenda and that former regime elements are exploiting both the politicians and the activists.

“There is unholy alliance among these groups. They have insisted on having one enemy and that is President Morsi,” he said.

Tamarod activists say it is they who are leading the politicians of the mainly liberal and secular opposition parties and factions, trying to drag them into a better connection with the public. The campaign’s plan calls for Morsi to leave, the chief justice of the Supreme Constitutional Court to become a largely symbolic interim president while a technocrat Cabinet governs, a panel would write a new constitution and presidential elections would be held in six months.

Ahmed Abdu, one of the first Tamarod street campaigners, said the group will pressure the opposition to coalesce behind a candidate.

If they can’t get organized “we will pick one away from all the top leaders of opposition and we will be able to rally support to him.”

He blamed liberal parties for running multiple candidates in last year’s presidential election, which resulted in a runoff between Morsi and a former Mubarak prime minister, forcing people to choose between an Islamist and a loyalist of the regime just ousted.

“I hope they don’t let us down again,” Abdu said.

Tamarod’s nationwide network and pavement-pounding methods contrast with many of the political parties, which have struggled to establish a nationwide presence. That is in large part what opened the way for the Muslim Brotherhood, an 83-year-old organization that has highly disciplined cadres nationwide, and harder-line Islamist with their own organizations to dominate parliament elections in late 2011-early 2012, to ensure the constitution passed a December referendum, and to boost Morsi to victory.

Tamarod’s volunteers — some former Morsi supporters, others who disliked him from the start — had varying stories of what brought them to the campaign. Most said they were dismayed by what they call the Brotherhood’s opportunism and determination to control the system rather than reform state institutions and police. That is a frequent refrain from critics of Morsi. His allies insist they are not trying to monopolize, that opponents have refused to work with them and that old regime loyalists have sabotaged their attempts at reform.

At the Tamarod office, Doaa Mohammed, a young Justice Ministry employee, said the day after Morsi’s election, a man on the street spit at her face and yelled, “Tomorrow, Morsi will get rid of you all.”

Mohammed wears a stylish scarf covering her hair, less strict than the more cloaking coverings and veils that hard-liners believe women should wear.

She said managers in her ministry were replaced by Brotherhood sympathizers.

“From day one, I have been treated like a second-class citizen. The Sister enjoys higher status than me just because she belongs to the group,” she said, referring to the Muslim Sisters, the women’s branch of the Brotherhood.

The heart of Tamarod is its petitions. Through Facebook and Twitter, volunteers could download the form, copy it and distribute them among friends and family members or hit the streets for signatures, then get back in touch with coordinators to return the papers.

At the Tamarod office, a psychology university lecturer-turned-volunteer explained how the papers are sorted by province, counted, scanned and entered into a database to ensure there are no doubled ID numbers and that the numbers — which have prefixes by province — match where they’re said to come from. Much of the work takes place in a room labeled “Control Room. No Entry.”

Secrecy is tight. The university lecturer spoke on condition of anonymity — he goes by the nickname “Maestro” — so he could not be singled out for pressure by anyone trying to get to the petitions. He said only two of the founders know the whereabouts of the originals of the signed forms and are responsible for moving them every few days to new locations.

“We are working in the daylight but they don’t want us to work in the daylight,” he said and added, “we are holding a pen and a paper. This is our weapon. And this is how we tell them, Enough”